1. FIELD OF THE INVENTION
This invention relates to a pneumatic apparatus for classifying particles of refuse material and the like, to separate relatively light and heavy solid particles. In particular, this invention relates to a column classifier through which air is drawn from bottom to top and which has a feed chute that opens into the column intermediate the top and bottom, for admitting mixed light and heavy solid particles to the rising air stream, with the heavier particles dropping from the column while lighter particles are carried upwardly in the air stream.
2. DESCRIPTION OF THE PRIOR ART
Pneumatic devices for classifying and separating solid particles in an apparatus that a column with a stream of air rising therethrough, are known to the prior art. To facilitate describing the distinguishing features of the present invention from the prior devices, such prior devices can be categorized as comprising two types. A first type includes a column in which mixed solid particles are dropped into the top of the column in which a stream of air is rising; and a second type includes a column in which mixed solid particles are fed at an intermediate elevation into the column in which air is rising.
Examples of apparatus of the first type appear in U.S. Pat. Nos. 1,465,884 of Aug. 21, 1923; 1,650,727 of Nov. 29, 1927; 1,787,759 of Jan. 6, 1931; and 3,833,117 of Sept. 3, 1974.
Examples of the second type appear in U.S. Pat. Nos. 2,968,400 of Jan. 17, 1961; 3,265,210 of Aug. 9, 1966; and 3,441,131 of Apr. 29, 1969.
As will appear from the description to follow, the present invention relates to the aforesaid second type. The present invention has for its object the control of the velocity and flow pattern of an air stream into which mixed size and weight particles of refuse are admitted for classification and separation to provide an improved control effect upon separation characteristics in that type of classifier-separator. In such regard, it should be noted that among the prior patents referred to, there is a disclosure of a column with a wall that is movable to vary the horizontal cross-sectional area of the column and as a result thereof provides adjustable velocity of air flow through the column. That is, U.S. Pat. No. 3,441,131, in FIGS. 10-12, discloses a vertical wall structure supported by bolt shanks movable in horizontal slots, to vary cross-sectional area and air flow velocity. In addition, applicants are aware that devices of the aforesaid second type have been built with a pivotally supported vertical wall swingable about a horizontal axis toward and away from a facing wall to vary the cross-sectional area therebetween. However, such a swinging motion elevates or lowers the lower-edge lip of the swinging wall relative to adjacent walls and changes the flow pattern of air drawn into the column.
None of the aforesaid practices of the prior art have involved a wall pivotal about a horizontal axis that is carried by an adjustably inclined member having an inner surface facing both downwardly and toward a feed inlet chute, to adjustably turn an upwardly moving air stream moving in a tortuous path, in a manner that will be described with regard to the present invention.